According to the principle of black body radiation, an object radiates a wide-band electromagnetic wave having a maximum value at a desired (or alternatively, a predetermined) wavelength based on a temperature of the object. For example, an object at room temperature radiates infrared rays having a maximum value in about a 10 μm wavelength band. A bolometer is a tool for measuring radiation energy radiated in the surroundings by absorbing an electromagnetic wave having a wavelength in an infrared (or terahertz) band, which is radiated according to the principle of black body radiation, converting the absorbed electromagnetic wave to heat, and detecting a temperature change due to the heat.
Recently, along with the development of microelectromechanical system (MEMS) technology, an infrared detector having a plurality of microbolometers arranged in a two-dimensional array has been produced. The infrared detector may be used for acquiring thermal images, for example, in thermal image cameras and the like.
A bolometer of the Salisbury screen method, which has a λ/4 spacing between a ground flat board and a thermal absorber (λ denotes a central wavelength of an infrared wavelength band to be detected) may be utilized in the thermal image camera. To implement a thermal image camera having high temperature accuracy at high resolution, the size of each pixel may be miniaturized.